When shopping for a new battery you will notice that there are some batteries that are labeled "OEM" and some that are not. You will also notice the significant price difference between the two. Most people assume that since the OEM batteries are more expensive, they are much higher quality batteries, but this isn't necessarily the case.
OEM stands for Original Equipment Manufacturer, so when looking at batteries, you will see the specific brand name like "Motorola" or "Samsung" or "Blackberry". These are the batteries your phone originally comes with and Just like any other product you buy, you have to decide whether you want to pay for the slightly overpriced quality brand name item, or the much cheaper but slightly lesser quality generic item.
Milliamps an hour is the unit for measuring the total amount of energy a battery can store at a time, or more simply, how long your battery will last you. When you are looking at batteries, you will probably see a bunch of confusing numbers, but this is the rating that really matters. Keep in mind that this isn't a measurement of time, it really depends on how often you are using your phone and how you are using it. But you can compare this rating with one of your original batteries, so that you can get a better feel of how much battery life you are going to get.
For example, if your original battery is 800 mAh and the replacement battery you choose is 900 mAh, you can expect that this battery will give you more battery life than the original one.
Extended batteries are batteries that have a much higher mAh rating so they will give you significantly more battery life for your cell phone, sometimes it's even double. But remember that the physical size of the battery is going to be slightly larger than your original battery, so you will need an extended door in order for the extended battery to fit.
Some extended batteries come with this door, but some of them do not so it' s something to take into consideration when purchasing an extended battery.
If you receive your battery and the charge is not holding as well as it should be, you might need to cycle the battery. This is a technique used on many types of batteries in order to prolong the life of the battery. The process is simple; all you have to do is use your phone until it is completely dead and turns off, then charge the battery over night or until the power is at 100%. Then repeat this about 3 or 4 times. If you do not cycle the battery sometimes the lithium battery might lose its ability fully recharge.
So that's all you need to know when you go to purchase a replacement or extended battery for your phone.